homooligomere

Homooligomere, also spelled homooligomer, is a molecular assembly composed of multiple copies of the same polypeptide or subunit. In a homooligomere, all subunits are identical in sequence and structure, in contrast to heterooligomeres that contain different subunits. Homooligomeric assemblies are common in enzymes, transporters, and structural complexes, and can range from dimers to icosahedral-like multimers.

Examples include the E. coli chaperonin GroEL, which forms a double-ring complex of identical subunits (a 14-mer), and lumazine synthase, which can assemble into a 60-subunit homo-oligomer. Some proteins assemble as cyclic or symmetric homo-oligomers (for example homotetramers, homohexamers). The symmetry of homooligomers influences cooperativity, allostery, and stability, enabling coordinated function and compact packing of subunits.

Determination of the oligomeric state is important in biochemistry and structural biology and is investigated by techniques such as size-exclusion chromatography, analytical ultracentrifugation, cross-linking, native mass spectrometry, and cryo-electron microscopy. Understanding whether a protein forms a homooligomer can inform interpretations of its mechanism, regulation, and interactions, and it has implications for drug design and protein engineering.